There are special potties made for Tisha B’av which is 11 inches high and conforms to halacha. At Eichler’s, they can be found next to the Shabbos bathroom paper and across the aisle from the chametz packets which sell for only $1.99 each. They are wonderful as the ten pieces come individually double wrapped and you get the b’racha included as well. America, what a wonderful country!
